The epileptic state is probably initiated by small, subtle changes in membrane characteristics of neurons within the involved area. These small changes are then amplified by means of the recurrent, positive feedback system of the involved neuronal population. The net result of this great amplification of small changes in membrane activity is the paroxysmal state. Studies of neurons within experimental epileptic foci have thus far failed to establish the nature of these 'trigger' mechanisms, presumably because they cannot be recognized in a system as complex as the mammalian cortex. This study will concern itself, therefore, with a detailed examination of the effect of convulsant agents on selected characteristics of the neuronal membrane and neuronal transmission in isolated neuronal preparations. We will also investigate the activity of some anticonvulsant drugs on similar preparations both untreated and pretreated with convulsive agents.